The present application relates to back-end-of-the-line (BEOL) semiconductor technology. More particularly, the present application relates to BEOL interconnect structures that have enhanced electromigration (EM) resistance and a controlled via resistance and methods of forming the same.
Generally, semiconductor devices include a plurality of circuits which form an integrated circuit fabricated on a semiconductor substrate. A complex network of signal paths will normally be routed to connect the circuit elements distributed on the surface of the substrate. Efficient routing of these signals across the device requires formation of multilevel or multilayered schemes, such as, for example, single or dual damascene wiring, i.e., interconnect, structures.
Within typical dual damascene interconnect structures, electrically conductive metal vias run perpendicular to the semiconductor substrate and electrically conductive metal lines run parallel to the semiconductor substrate. Typically, the electrically conductive metal vias are present beneath the electrically conductive metal lines and both features are embedded within an interconnect dielectric material layer.
In conventional dual damascene interconnect structures, copper or a copper containing alloy has been used as the material of the electrically conductive metal vias and lines. In recent years, advanced dual damascene interconnect structures containing a combined electrically conductive via/line feature have been developed in which an alternative metal such as cobalt or ruthenium has been used instead of copper or a copper alloy in the electrically conductive via only, or in both the electrically conductive via and electrically conductive line. While the use of such alternative metals in the via can provide enhanced electromigration resistance, such advanced dual damascene structures exhibit a significant via resistance increase. In instances when the alternative metal replaces the copper or copper alloy line, reduced metal line resistance can be observed.
There is thus a need for providing advanced dual damascene interconnect structures in which an alternative metal can be used in at least the electrically conductive via without significant impact on the via resistance of the interconnect structure.